Methods and devices for cutting tissue

ABSTRACT

A catheter is provided, which includes a cutting element having one or more raised elements. The cutting element has a cup-shaped surface at the distal end that may be smooth and continuous except for the raised elements.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. Ser. No. 14/280,713, filedMay 19, 2014, which is a continuation of U.S. Ser. No. 12/325,797 filedDec. 1, 2008, now U.S. Pat. No. 8,787,440, which is a continuation ofU.S. Ser. No. 12/283,224 filed Sep. 9, 2008, which claims the benefit ofprovisional application Ser. No. 61/067,238, filed Feb. 25, 2008, thecontents of each of which arc hereby incorporated herein by reference.

BACKGROUND

Atherectomy catheters are used to remove material from a blood vessel toopen the blood vessel and improve blood flow through the vessel.

One problem that occurs when removing material from a blood vessel isthat the material may be either soft or hard and may vary during thecutting process. As such, the cutting element should be able to cut bothhard tissue and soft tissue.

The present invention is directed to a cutting element for anatherectomy catheter and methods of cutting material from a blood flowlumen using a rotating cutting element.

SUMMARY

The present invention provides an atherectomy catheter, which has acutting element that is able to cut both soft tissue and hard tissue.The cutting element has a sharp cutting edge that surrounds a cup shapedsurface. The cup-shaped surface directs the material, which has been cutinto a tissue chamber. The circumferential cutting edge and thecup-shaped surface together are well suited to cut and remove relativelysoft tissue.

In one aspect of the invention, an atherectomy catheter is providedwhich has one or more raised elements extending from the cup-shapedsurface. The raised element may be recessed longitudinally and radiallyfrom the outer cutting edge by a controlled distance such as0.0010-0.0020 inch but may, of course, be closer or briber from theouter cutting edge depending upon the application. The raised elementshelp to break up had tissue such as calcified plaque. The raisedelements are somewhat recessed from the distal end so that the cuttingedge remains exposed to cut soft tissue. When the cutting elementencounters tissue, which is too hard to be cut sufficiently by thecutting edge, the raised elements help to break the harder tissue with amore blunt application of force.

In another aspect of the invention, the raised element is somewhat smallso that a relatively large portion of the cup-shaped surface is smoothand uninterrupted. In this manner, the ability of the cutting element todirect tissue into the tissue chamber with the cup-shaped surface is notoverly inhibited by the raised elements. For example, the raisedelements may occupy an area less than 60 degrees when viewed along thelongitudinal axis. Stated another way, the cup-shaped surface of thecutting element is smooth and uninterrupted throughout at least 300degrees when viewed along the longitudinal axis. Stated still anotherway, the cup-shaped surface may be smooth and uninterrupted for at least95% of the surface area of the cutting element when viewed along thelongitudinal axis.

These and other aspects will become apparent from the followingdescription of the preferred embodiments, drawings and claims.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a distal end of an atherectomy catheter.

FIG. 2 is a cross-sectional view of the atherectomy catheter with acutting element in as stored position.

FIG. 3 is a cross-sectional view with a cutting element in a workingposition;

FIG. 4 shows an embodiment of a cutting element;

FIG. 5 shows an end view of an embodiment of a cutting element;

FIG. 6 is a cross-sectional view of an embodiment of a cutting element;

FIG. 7 shows another embodiment of a cutting element which may be usedwith the atherectomy catheter;

FIG. 8 shows the embodiment of the cutting element of FIG. 7 and FIG. 8Ashows one of the raised elements of the cutting element embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1-4, an atherectomy catheter 2 is shown which has acutting element 4, which is used to cut material from a blood flowlumen. The cutting element 4 is movable between a stored position (FIG.2) and a cutting position (FIG. 3) relative to an opening 6 in a body 8of the catheter 2. The cutting element 8 moves outwardly relative to theopening 6 so that a portion of the element 4 extends outwardly from thebody 8 through the opening 6. The cutting element 4 may be positionedrelative to the body 8 and opening 6 so that less than 90 degrees of thecutting element 4 is exposed to cut tissue. Of course, more of thecutting element 4 may he exposed without departing from numerous aspectsof the invention.

The catheter 2 is moved distally through a vessel with the cuttingelement 4 in the working or cutting position as described in furtherdetail below. As the catheter 2 moves through the blood vessel, thetissue is cut by the cutting element 4 and is directed into a tissuechamber 12 positioned distal to the cutting element 4. The tissuechamber 12 may be somewhat elongate to accommodate the tissue, which hasbeen cut.

The cutting element 4 is moved proximally from the stored position sothat a cam surface 14 on the cutting element 4 engages a ramp 16 on thebody 8 of the catheter 2. The interaction between the cam surface 14 andthe ramp 16 causes the cutting element 4 to move to the cutting positionand also causes a tip 18 to deflect which tends to move the cuttingelement 4 toward the tissue to be cut.

The cutting element 4 is coupled to a shaft 20 that extends through alumen 21 in the catheter 2. The cutting element 4 is rotated about alongitudinal axis LA when the shaft rotates. The cutting element 4 isrotated about 1 to 160,000 rpm but may be rotated at any other suitablespeed depending upon the particular application.

Referring to FIGS. 2, 4 and 5, the cutting element 4 is shown whenviewed along the longitudinal axis LA. The term “along the longitudinalaxis” as used herein shall mean the view of FIG. 5 that shows the distalend of the cutting element 4 when viewed in the direction of thelongitudinal axis and/or the axis of rotation. The cutting element 4 hasa cutting edge 22 that may be a continuous, uninterrupted,circular-shaped edge although it may also include ridges, teeth,serrations or other features without departing from the scope of theinvention. The cutting edge 22 may be at a radially outer edge 23 of thecutting element 4 when the cutting element 4 is in the cutting position.

The cutting element 4 has a cup-shaped surface 24, which directs thetissue cut by the cutting edge 22 into the tissue chamber 12. Thecup-shaped surface 24 may be a smooth and continuous surface free ofthroughholes, teeth, fins or other features, which disrupt the smoothnature of the surface 24 for at least half the distance from thelongitudinal axis LA to the outer radius at the cutting edge 22. Thecup-shaped surface 24 may also be free of any such features throughoutan area of at least 300 degrees relative to the longitudinal axis LA.

Referring to FIG. 4-6, one or more raised elements 26 extend outwardlyfrom the cup-shaped surface 24 with FIG. 5 showing two raised elements26. The raised element 26 is a small wedge of material that risesrelatively abruptly from the cup-shaped surface 24. The raised element26 has a first wall 30 and a second wall 32 that both extend radiallyand form an angle of about 20 degrees therebetween so that the tworaised elements 26 together occupy an area of about 40 degrees andaltogether may be less than 60 degrees. A third wall 34 extends betweenthe radially inner portion of the first and second walls 30, 32. Theraised element 26 helps to break up hard tissue and plaque by applying arelatively blunt force to the hard tissue or plaque since cutting suchtissue with the cutting edge 22 is often not effective.

The raised elements 26 altogether occupy a relative small part of thecup-shaped surface 24. The raised elements 26 together may occupy lessthan 5% of as surface area of the cutting element 4. The term “surfacearea of the cutting element” as used herein shall mean the surface areawhich is radially inward from the outer or cutting edge 22 and isexposed when viewed along the longitudinal axis LA. Stated another way,at least 95% of the surface area of the cutting element is a smoothcup-shaped surfaced when viewed along the longitudinal axis. By sizingand positioning the raised element 26 in this manner, the raised element26 does not interfere with the ability of the cutting element 4 to cutand re-direct tissue into the tissue chamber while still providing theability to break up hard tissue and plaque with the raised element 26.

The raised element 26 may be recessed from the cutting edge 22longitudinally and/or radially. The raised element 26 may be recessedlongitudinally from the cutting edge 0.0010 to 0.0020 inch and may beabout 0.0015 inch. The raised element 26 may be recessed radially fromthe cutting edge 22 by about the same amount. A distal wall 38 of thecutting element 4 forms a flat surface 40, which is perpendicular to thelongitudinal axis LA so that the entire surface is recessed the samedistance from the cutting edge. The distal wall 38 may take any othershape, such as a curved shape, or may be tilted, inclined or beveled asnow described.

Referring to FIGS. 7, 8 and 8A, another cutting element 4A is shownwherein the same or similar reference numbers refer to the same orsimilar structure and all discussion concerning the same or similarfeatures of the cutting element 4 are equally applicable here. Thecutting element 4A has a cutting edge 22A that may be a continuous,uninterrupted, circular-shaped edge although it may also include ridges,teeth, serrations or other features without departing from the scope ofthe invention. The cutting edge 22A may he at a radially outer edge 23Aof the cutting element 4A when the cutting element 4A is in the cuttingposition. The cutting element 4A has a cup-shaped surface 24A thatdirects the tissue cut by the cutting edge 22A into the tissue chamber12 (see FIG. 2). The cup-shaped surface 24A may be a substantiallysmooth arid continuous surface as described shove in connection with thecutting element 4.

One or more raised elements 26A, extend outwardly from the cup-shapedsurface 24A. FIG. 8 shows four raised elements 26A but may include anynumber such as 2, 3, 4, 6 or 8 raised elements. The raised clement 26Ais a small wedge of material that rises relatively abruptly from thecup-shaped surface 24A. The raised element 26A has a first wall 30A anda second wall 32A which both extend radially and form an angle of about1 to 30 degrees therebetween so that the four raised elements 26Atogether occupy an area of about 4 to 60 degrees and altogether may beless than 60 degrees altogether. A third wall 34A extends between theradially inner portion of the first and second walls 30A, 32A. Theraised elements 26A may occupy a relative small part of the cup-shapedsurface 24A and may be recessed from the cutting edge 22A in the mannerdescribed above in connection with the cutting element 4.

A distal wall 38A of the cutting element 4A has a surface 40A that formsan angle of about 30-90 degrees with respect to the longitudinal axisLA. The entire surface 40A may still be somewhat close to but recessedfrom the cutting edge 22A so that the entire surface 40A is 0.0010 to0.0050 inch from the cutting edge. An edge 50 formed at the intersectionof wall 30A and distal wall 38A is closer to the cutting edge 22A thanan edge 52 formed at the intersection of wall 32A and distal wall 38A.The cutting element 4A may be rotated in either direction so that theraised edge 50 may be the leading or trailing edge. The raised edge maybe 0.0010 to 0.0020 inch from the cutting edge. The raised elements 26Amay all be formed in the same manner or may be different from oneanother. For example. some of the elements 26A could be angled indifferent directions so that two of the elements have the raised edge 50as the leading edge and two of the elements 26A have the raised edge 50as the trailing edge. The raised elements 26A may also subtend differentangles, be of different heights or may have different radial lengthswithout departing from various aspects of the present invention.

Use of the catheter 2 is now described in connection with the cuttingelement 4 but is equally applicable to use of the catheter 2 with thecutting element 4A. The catheter 2 is introduced into the patient in aconventional manner using a guidewire (not shown) or the like. Thecatheter 2 is advanced with the cutting element in the stored positionof FIG. 2 until the catheter is positioned at the location wherematerial is to be removed. The cutting element 4 is then movedproximally so that the ramp 16 and cam surface 14 engage to move thecutting element 4 to the cutting position of FIG. 3 and to deflect thetip of the catheter 2. to move the cutting element 4 toward the tissue,to be cut. The cutting element 4 is rotated about longitudinal axis LAand catheter 2 is then moved distally through the vessel so that thecutting element 4 cuts tissue. The tissue, which has been cut, isdirected into the tissue chamber 12.

The present invention has been described in connection with preferredembodiments but may, of course, be practiced while departing from theabove described embodiments. For example, three or more raised elementsmay be provided or cutting edge may be serrated without departing fromnumerous aspects of the present invention.

What is claimed is:
 1. An atherectomy catheter, comprising: a bodyhaving opposite proximal and distal ends; a rotatable shaft coupled tothe body; a cutting element adjacent the distal end of the body andcoupled to the rotatable shaft, such that the rotatable shaft is able torotate the cutting element through a complete rotation about alongitudinal axis of the cutting element, the cutting element havingopposite first and second longitudinal ends, a cutting edge extendingcircumferentially at the first longitudinal end of the cutting element,and an interior surface recessed longitudinally from the cutting edge;and a raised element extending longitudinally outward from the interiorsurface of the cutting element toward the first longitudinal end of thecutting element, the raised element having a first side wall extendinginward from the interior surface generally toward the longitudinal axisof the cutting element, and a longitudinal end wall defining alongitudinal end surface of the raised element which intersects thefirst side wall to form a first raised edge of the raised element,wherein the raised element further has a second side wall extendinginward from the interior surface generally toward the longitudinal axisof the cutting element, wherein the longitudinal end surface of theraised element intersects the second side wall to form a second raisededge of the raised element.
 2. The catheter of claim 1, wherein thelongitudinal end surface of the raised element forms an angle from 30degrees to 90 degrees with respect to the longitudinal axis of thecutting element.
 3. The catheter of claim 1, wherein the first raisededge has inner and outer ends relative to the longitudinal axis of thecutting element, wherein the inner end of the first raised edge isspaced radially inward from the cutting edge a distance of 0.0010 in(0.0254 mm) to 0.0020 in (0.0508 mm).
 4. The catheter of claim 1,wherein the first raised edge has inner and outer ends relative to thelongitudinal axis of the cutting element, wherein the outer end of thefirst raised edge is recessed longitudinally from the cutting edge. 5.The catheter of claim 4, wherein the first raised edge has inner andouter ends relative to the longitudinal axis of the cutting element,wherein the outer end of the first raised edge is recessed from thecutting edge by a longitudinal distance of 0.0010 in (0.0254 mm) to0.0020 in (0.0508 mm).
 6. The catheter of claim 1, wherein the secondraised edge is recessed longitudinally relative to the first raisededge.
 7. The catheter of claim 1, wherein the rotatable shaft isconfigured to rotate the cutting element so that the first raised edgeis the leading edge and the second raised edge is the trailing edge. 8.The catheter of claim 1, wherein the raised element further has an innerwall extending between and intersecting the first and second side wallsand the longitudinal end wall and the interior surface of the cuttingelement, respectively.